The present invention relates to a lithography process used to fabricate semiconductor devices.
FIG. 1 is a simplified cross-sectional view illustrating conventional box-in-box type alignment marks.
FIGS. 2a through 2e are simplified cross-sectional views illustrating a conventional method for forming an alignment mark, wherein FIGS. 2a(ii) through 2e(ii) are cross-sectional views taken along the line I-I′ of FIG. 1.
Referring to FIGS. 2a and 2b, a stacked structure of an etch stop nitride film 30 and an interlayer insulating film 40 is formed over a semiconductor substrate 10 having a lower structure such as a storage node contact plug 20 and a bit line 25 in a cell region 1000a and a scribe region 1000b. A predetermined region of the interlayer insulating film 40 and the etch stop nitride film 30 is etched to form a storage node region 45 in the cell region 1000a and an alignment mark region 47 in the scribe region 1000b. A layer for storage node 50 is formed over an entire surface of the resulting structure including the storage node region 45 in the cell region 1000a and the alignment mark region 47 in the scribe region 1000b. 
Referring to FIGS. 2c and 2d, the layer for storage node 50 is planarized until the interlayer insulating film 40 is exposed to separate a storage node 55 from its neighboring storage node 55. A photoresist film (not shown) is formed to cover the cell region 1000a including the storage node region 45 shown in FIG. 2a. The layer for storage node 50 in the scribe region 1000b is removed.
Referring to FIG. 2e, the photoresist film is removed. The interlayer insulating film 40 is removed to form a cylindrical capacitor 60 in the cell region 1000a and an alignment mark 65 in the scribe region 1000b. 
FIGS. 3a and 3b are photographs according to the conventional method for forming a semiconductor device. After the process for removing the layer for storage node 50 in the scribe region 1000b shown in FIG. 2d, a conductive particle is placed over the storage node 55 shown in FIG. 2d, and a residue of the conductive particle remains at a sidewall of the alignment mark 65 shown in FIG. 2e. 
According to the above conventional method for forming an alignment mark, during a process for forming the cylindrical capacitor, the residue of the conductive particle remains at the sidewall of the alignment mark, which causes the conductive particle to be placed over the capacitor. As a result, the capacitor of the device may fail. Accordingly, there is a need to perform an additional process for removing a remaining conductive material in the scribe region, which is called a POM (Peri open mask) process.